A Compact and Broadband Photonic Crystal Fiber Polarization Filter Based on a Plasmonic Resonant Thin Gold Film

Abstract

A novel high birefringence gold-coated photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance is proposed. The six elliptical holes arranged in a specific mode surrounding the core are utilized to gain high birefringence, and gold is coated inside the air holes to generate surface plasmons. By improving structural parameters, we achieve one state of polarization to propagate through the filter whereas the other state is severely attenuated. Specially, in the 1550 nm communication band, the confinement loss of y-polarized mode can reach 442 dB/cm while the corresponding loss of x-polarized mode is only 0.0316 dB/cm. The distinction between two losses is more than 10 000 times. In addition, when the length of the designed PCF filter is 1 mm, an extinction ratio of 326 dB/cm is obtained. The applicable bandwidth is up to 300 nm while the fiber length is merely 50 μm, which is better than other reported literatures. Owing to above-mentioned characteristics, the proposed polarization filter can be widely applied in compact and broadband filters in the communication band.

Surface Plasmon Resonance Sensor Based on Dual-Side Polished Microstructured Optical Fiber with Dual-Core

“…The thickness of a gold film is the most important factor that affects the SPR spectra and thus the sensing performance [ 8 , 9 , 10 , 12 , 13 , 15 , 16 , 18 , 24 , 33 , 34 , 35 , 36 ]. Figure 6 shows the loss spectra of the x -even core modes by varying m for n a = 1.44 and 1.45.…”

“…The mode characteristics and the sensing performance of the proposed sensor were simulated through commercially available software COMSOL. A perfectly matched layer (PML) was added to the outer computational region, which was applied to absorb scattered light [ 9 , 10 , 15 , 16 , 18 , 19 , 25 , 26 , 27 , 28 , 29 , 31 , 36 , 37 , 38 ].…”

“…The RI of the air was set to 1. To achieve the dielectric constant of gold (ε( ω )), we used the Drude–Lorentz model, of which the equation can be written as follows [ 48 ]: where ε ∞ is the permittivity at high frequencies, ω can be interpreted as the angular frequency, ω D and γ D indicate the plasma frequency and the damping frequency, respectively, Δε is the weighting factor, and Γ L and Ω L are the spectral width and the oscillator strength of the Lorentz oscillators, respectively [ 10 , 34 , 36 , 48 ].…”

“…To alleviate phase-matching problems of optical fiber-based SPR sensors, microstructured optical fiber (MOF)-based SPR sensors have been widely studied owing to their design flexibility [ 9 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. By changing the size, shape, and arrangement of air holes along the propagation direction, the n eff can be tuned to the anticipated values and thus can solve the phase-matching problem between the core mode and the SPP mode [ 9 , 15 , 16 , 17 , 24 , 25 ].…”

Research on the Theory of Optical Transmission for Bragg Fiber With High-Index-Core

“…The formation mechanism of the energy band in the photonic crystal is similar to the earlier mentioned process. The propagation of the electromagnetic wave in medium satisfies Maxwell equation [13][14][15][16]…”